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Register a new userNew physics explanations of $a_mu$ in light of the FNAL muon $g-2$ measurement
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The Fermilab Muon $g-2$ experiment recently reported its first measurement of the anomalous magnetic moment $a_mu^{textrm{FNAL}}$, which is in full agreement with the previous BNL measurement and pushes the world average deviation $Delta a_mu^{2021}$ from the Standard Model to a significance of $4.2sigma$. Here we provide an extensive survey of its impact on beyond the Standard Model physics. We use state-of-the-art calculations and a sophisticated set of tools to make predictions for $a_mu$, dark matter and LHC searches in a wide range of simple models with up to three new fields, that represent some of the few ways that large $Delta a_mu$ can be explained. In addition for the particularly well motivated Minimal Supersymmetric Standard Model, we exhaustively cover the scenarios where large $Delta a_mu$ can be explained while simultaneously satisfying all relevant data from other experiments. Generally, the $Delta a_mu$ result can only be explained by rather small masses and/or large couplings and enhanced chirality flips, which can lead to conflicts with limits from LHC and dark matter experiments. Our results show that the new measurement excludes a large number of models and provides crucial constraints on others. Two-Higgs doublet and leptoquark models provide viable explanations of $a_mu$ only in specif
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Gluino-SUGRA ($tilde{g}$SUGRA), which is an economical extension of mSUGRA, adopts much heavier gluino mass parameter than other gauginos mass parameters and universal scalar mass parameter at the unification scale. It can elegantly reconcile the experimental results on the Higgs boson mass, the muon $g-2$, the null results in search for supersymmetry at the LHC and the results from B-physics. In this work, we propose several new ways to generate large gaugino hierarchy (i.e. $M_3gg M_1,M_2$) for $tilde{g}$SUGRA model building and then discuss in detail the implications of the new muon $g-2$ results with the updated LHC constraints on such $tilde{g}$SUGRA scenarios. We obtain the following observations: (i) For the most interesting $M_1=M_2$ case at the GUT scale with a viable bino-like dark matter, the $tilde{g}$SUGRA can explain the muon $g-2$ anomaly at $1sigma$ level and be consistent with the updated LHC constraints for $6geq M_3/M_1 geq 9$ at the GUT scale; (ii) For $M_1:M_2=5:1$ at the GUT scale with wino-like dark matter, the $tilde{g}$SUGRA model can explain the muon $g-2$ anomaly at $2sigma$ level and be consistent with the updated LHC constraints for $3geq M_3/M_1 geq 4$ at the GUT scale; (iii) For $M_1:M_2=3:2$ at the GUT scale with mixed bino-wino dark matter, the $tilde{g}$SUGRA model can explain the muon $g-2$ anomaly at $2sigma$ level and be consistent with the updated LHC constraints for $6.7geq M_3/M_1 geq 7.8$ at the GUT scale.
After a brief review of the muon g-2 status, we discuss hypothetical errors in the Standard Model prediction that might explain the present discrepancy with the experimental value. None of them seems likely. In particular, a hypothetical increase of the hadroproduction cross section in low-energy e+e- collisions could bridge the muon g-2 discrepancy, but it is shown to be unlikely in view of current experimental error estimates. If, nonetheless, this turns out to be the explanation of the discrepancy, then the 95% CL upper bound on the Higgs boson mass is reduced to about 135GeV which, in conjunction with the experimental 114.4GeV 95% CL lower bound, leaves a narrow window for the mass of this fundamental particle.
After a brief review of the muon g-2 status, we discuss hypothetical errors in the Standard Model prediction that could explain the present discrepancy with the experimental value. None of them looks likely. In particular, an hypothetical increase of the hadroproduction cross section in low-energy e^+e^- collisions could bridge the muon g-2 discrepancy, but is shown to be unlikely in view of current experimental error estimates. If, nonetheless, this turns out to be the explanation of the discrepancy, then the 95% CL upper bound on the Higgs boson mass is reduced to about 130 GeV which, in conjunction with the experimental 114.4 GeV 95% CL lower bound, leaves a narrow window for the mass of this fundamental particle.
We study the constraints imposed by perturbative unitarity on the new physics interpretation of the muon $g-2$ anomaly. Within a Standard Model Effective Field Theory (SMEFT) approach, we find that scattering amplitudes sourced by effective operators saturate perturbative unitarity at about 1 PeV. This corresponds to the highest energy scale that needs to be probed in order to resolve the new physics origin of the muon $g-2$ anomaly. On the other hand, simplified models (e.g.~scalar-fermion Yukawa theories) in which renormalizable couplings are pushed to the boundary of perturbativity still imply new on-shell states below 200 TeV. We finally suggest that the highest new physics scale responsible for the anomalous effect can be reached in non-renormalizable models at the PeV scale.
The new FNAL result of the muon $g-2$, combined with the BNL result, shows a 4.2$sigma$ deviation from the SM. We use the new data of the muon $g-2$ to revisit several GUT-scale constrained SUSY models with the constraints from the LHC searches, the dark matter detection, the flavor data and the electroweak vacuum stability. We first demonstrate the tension between the muon $g-2$ and other experimental measurements in the CMSSM/mSUGRA. Then after discussing the possible ways to alleviate such a tension and showing the muon $g-2$ in pMSSM under relevant experimental constraints, we survey several extensions of the CMSSM/mSUGRA with different types of universal boundary conditions at the GUT scale. Finally, we briefly discuss the muon $g-2$ in other popular SUSY breaking mechanisms, namely the GMSB and AMSB mechanisms and their extensions.
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